This project is being conducted by the University of New Mexico, Albuquerque, and the Los Alamos Scientific Laboratory (Clinton P. Anderson Meson Physics Facility) at Los Alamos, New Mexico, in preparation for clinical trials of pion radiation therapy for patients with advanced cancer. The primary objective of this project is to provide, as soon as possible, information crucial to the radiotherapist for beginning clinical trials of pion radiation therapy. Specific objectives are: a. To develop, test, and apply methods of pion dosimetry that are essential to the radiobiology experiments and which will logically carry over into the early pilot trials and subsequent clinical trials of the efficacy of pion therapy for cancer patients. b. To employ appropriate quantitative cellular radiobiology techniques to establish the relative biological effectiveness (RBE), oxygen enhancement ratio (OER), and effects of dose fractionation of pions under radiation conditions and geometries most informative to the radiotherapist, and c. To observe in appropriate experimental animals early and late responses and radiopathology of normal and tumor tissues exposed to various segments of the pion beam path to assess acute effects and delayed sequelae as a function of dose and exposure.